details about reproduction of bacteriophages and their differences.

1. Reproduction of bacteriophages
By
Fathima Hameed

2. What is bacteriophages?
• Bacteriophages are virus that
infect bacteria is called as
bacteriophages.
• The bacteriophages attacks the
bacteria like E.coli are called as
coli phages / T phages.
• Ex; T7, M13, Λ phages

3. Reproduction/replication cycle
Bacteriophages exhibit two types of replication process.
1. Lytic cycle or virulent
2. Lysogenic cycle or temperate
Lytic cycle or virulent
Phages infects that bacterium and takeover the bacterium to make lots
of bacteriophages, then it kills the cell by lyses.
Lysogenic cycle or temperate
Phages infects that bacterium and inserts its DNA into bacterial
chromosomes, allowing the phage DNA (prophage) to be copied and
passed along with the cell’s own DNA.

4. 1. Lytic cycle
• The tail of the phage bind to the specific receptor on the surface
of the bacterial cell.Attachment
• The phage injects its DNA to the cytoplasm of the bacterial cell.
Entry
• Phage DNA is copied and their genes are expressed to make
proteins (capsid proteins)
DNA copying &
protein synthesis
• Starts capsid assembly and they are stuffed with DNA to make
lots of new phages.
Assembly of new
phages
• after the expression of genes for proteins, that poke holes in the
plasma membrane & cell wall. The holes let water flow in,
making the cell expand and burst.
Lysis

5. Lytic cycle

6. 2. Lysogenic cycle
• The tail of the phage bind to the specific receptor on the surface of
the bacterial cell.Attachment
• The phage injects its DNA to the cytoplasm of the bacterial cell.
Entry
• Phage DNA integrate or recombines with the particular part of
the bacterial chromosomes.Integration
• The integrated phage DNA(prophage) is not active, its genes
aren't expressed, and it doesn't drive production of new phages.
However, each time a host cell divides, the prophage is copied
along with the host DNA.
Cell division

7. Lysogenic cycle

8. Lysogenic cycle continue…,
 In some conditions, the prophage can
become active; come back out of the
bacterial chromosome & triggering the
remaining steps of the Lytic cycle (DNA
copying and protein synthesis, phage
assembly, and Lysis).

9. Difference between Lytic and
Lysogenic
S.No Lytic cycle Lysogenic cycle
1 Virulent Non virulent
2 Host damage Host not damaged
3 Viral DNA doesn’t integrate into host
DNA
Viral DNA integrate into host DNA
4 Host DNA is hydrolyzed Host DNA is not hydrolyzed
5 Doesn’t have prophage Has a prophage
6 Viral DNA is high Viral DNA is low
7 Short period Takes Longtime
8 Doesn’t allow genetic recombination in
the host bacterium
It allows genetic recombination in the host
bacterium

10. Thank you